関連ワード:  define isotopes with example class 9    explain isotopes with example class 9    define radioisotopes with example class 9    isotopes definition with example class 9    define isotopes and isobars with example class 9    explain isotopes and isobars with example class 9    what are isotopes give one example class 9    what are isotopes give two examples class 9    define isotopes with example write two uses of isotopes class 9    what is isotopes class 9